ARCTIC

VOL. 59, NO. 3 (SEPTEMBER 2006) P. 319–321

Ross’s Gull (Rhodostethia rosea) Breeding in Penny Strait, Nunavut, CanadaMARK L. MALLORY,1 H. GRANT GILCHRIST2 and CAROLYN L. MALLORY 3

(Received 6 September 2005; accepted in revised form 18 November 2005)

ABSTRACT. We found a small, previously undiscovered breeding colony of Ross’s gulls (Rhodostethia rosea) in Nunavut,Canada, approximately 80 km from a previous colony location occupied during the 1970s. The birds nested in association witharctic terns (Sterna paradisaea). The collective observations from this region of the High Arctic suggest that Ross’s gulls maymove colonies each year, or that colony occupation is intermittent.

Key words: Ross’s gull, Rhodostethia rosea, Arctic, Canada

RÉSUMÉ. Nous avons repéré une petite colonie de reproduction de mouettes rosées (Rhodostethia rosea) non découverte jusqu’àce moment-là au Nunavut, au Canada, à environ 80 kilomètres de l’emplacement d’une autre colonie occupée dans les années1970. Les oiseaux nichaient avec des sternes arctiques (Sterna paradisaea). Les observations collectives de cette région del’Extrême-Arctique laissent supposer que les mouettes rosées peuvent changer de colonie chaque année ou que l’occupation descolonies est intermittente.

Mots clés : mouette rosée, Rhodostethia rosea, Arctique, Canada

Traduit pour la revue Arctic par Nicole Giguère.

1 Canadian Wildlife Service, P.O. Box 1714, Iqaluit, Nunavut X0A 0H0, Canada; mark.mallory@ec.gc.ca2 Canadian Wildlife Service, National Wildlife Research Centre, Raven Road, Carleton University, Ottawa, Ontario K1A 0H3, Canada3 Artemesia Consulting, P.O. Box 1261, Iqaluit, Nunavut X0A 0H0, Canada

© The Arctic Institute of North America

INTRODUCTION

Ross’s gull (Rhodostethia rosea) is the rarest breeding gullin North America, where only three breeding locationshave been confirmed: Cheyne Islands, Nunavut(MacDonald, 1978); Churchill, Manitoba (Chartier andCooke, 1980); and Prince Charles Island, Nunavut (Béchetet al., 2000). Like the ivory gull (Pagophila eburnea), thisspecies is usually associated with polar environments(Blomqvist and Elander, 1981; Hjort, 1982). Nesting colo-nies are typically small (< 25 pairs), and Ross’s gulls areoften found nesting in association with arctic terns (Sternaparadisaea; Buturlin, 1906; Densley, 1991; Béchet et al.,2000).

Although few colonies have been found, Ross’s gullsare regularly observed during fall migration near PointBarrow, Alaska, and sporadically along the Pacific andAtlantic coasts, as well as the Great Lakes, during the non-breeding season (Macey, 1981; Alvo et al., 1996). Many ofthese birds probably migrate from the main breeding areain Siberia (Buturlin, 1906) or the scattered, small coloniesknown outside of Siberia (Kampp and Kristensen, 1980;Blomqvist and Elander, 1981), but some may also origi-nate from North American sites that remain undiscovered.

As part of the research and monitoring of marine birdsin High Arctic Canada (Mallory and Gilchrist, 2003, 2005),we conducted surveys for Ross’s gulls at previous orpotential colony locations in Nunavut. Here we report on

the discovery of a new colony location and briefly describethe nests and behaviours of the breeding birds.

METHODS

Surveys were conducted on islands in Penny Strait(Fig. 1) on 16 July 2002, 10 July 2003, 1 July 2004, and 2July 2005, using a Bell 206 L4 helicopter. Sea-ice cover-age in Penny Strait varied among years, being extensive in2003 and 2004 (> 70%), moderate in 2005 (50%), andminimal in 2002 (< 10%). In the extensive-ice years, icebridges connected many of the islands to other islands orto mainland coasts of Bathurst Island, potentially allowingarctic foxes (Alopex lagopus) to reach small breedingislands.

In 2002, we surveyed 16 small islands in the straitbetween 75.8˚ and 76.7˚ N, and between 95.6˚ and 102˚ W.We landed on most islands and conducted surveys on foot,but in a few cases islands were very small and barren, andwe surveyed these while hovering at approximately 10 maltitude. Two biologists divided the islands into sectionsand searched for Ross’s gulls and other bird species(Mallory and Gilchrist, 2003). In 2003 – 05, we resurveyedSeymour Island (76.8˚ N, 101.3˚ W), the Cheyne Islands(76.3˚ N, 97.5˚ W), and a small, unnamed island east ofCrozier Island (75.8˚ N, 96.3˚ W). All of these are small(up to 3 × 1 km) rocky islands (Seymour) or gravel reefs,

320 • M.L. MALLORY et al.

and all are located more than 5 km from the mainland coastof Bathurst Island.

RESULTS AND DISCUSSION

In 2002, 2003, and 2004, we did not observe Ross’sgulls at any of the islands, nor were any seen in flightduring our extensive surveys.

In 2005, no Ross’s gulls were found at Seymour Islandor the Cheyne Islands, but several were observed near acolony of approximately 100 pairs of arctic terns andseven pairs of Sabine’s gulls (Xema sabini) on the un-named island. We found three Ross’s gull nests at approxi-mately 10, 25, and 40 m from the periphery of this maincolony of terns and gulls, and a fourth nest on the central,elevated gravel ridge running the length of the island.Intense adult defensive behaviour indicated a fifth nest25 m away on the ridge top, but we could not locate it. Noother species were nesting within 3 m of any Ross’s gullnest. Each nest cup was circular, approximately 12 cm indiameter, and was scraped into the gravel 30 mm deep onpebbles typically 1–2 cm in diameter, but was otherwiseunlined with nesting material. Three nests had two eggs,and one nest had three eggs (mean 2.25 ± 0.5 SD eggs).One egg that we found measured 42 × 30 mm, about thesame size as the eggs of the nearby terns. The eggs had adark, dull olive green colour similar to that of Sabine’s gulleggs, except that the sepia brown on the poles took theform of one continuous blotch around the pole, instead ofthe speckling of the Sabine’s gull egg.

Most of the gulls exhibited vigorous, tern-like nestdefense, with birds lifting off their nests when people were

over 20 m away, and then circling 10 m above the nest andemitting the “colony contact” call (Densley, 1991). Whenwe stopped at two of the nests, the resident pair dived closeto our heads (~ 1–2 m), emitting loud, rapid, high-pitchedcalls. However, the defense was less vigorous than thatexhibited by Sabine’s gulls (Day et al., 2001), which werelouder and approached more closely in their dives.

This site, which represents the fourth known nestinglocation of Ross’s gulls in North America (Fig. 1), isapproximately 80 km from the Cheyne Islands, where thespecies nested in 1976 and 1978 (MacDonald, 1978).Macey (1981) reported that MacDonald found no nests inthe Cheyne Islands in 1977 or 1979, but he did observebirds there in 1974 and 1979. In 2002–05, we failed to findnesting birds at the Cheyne Islands or on any other suitableislands within 50 km of this location. We also did not findany birds nesting at this new colony on the unnamed islandin 2002–04. Our surveys, and the previous reconnaissanceby MacDonald, suggest that colony occupation by Ross’sgulls is more intermittent in the Canadian High Arctic thanfarther south (Macey, 1981; Densley, 1991). In the north-ern locations, birds may move nesting locations each year,perhaps as a strategy to avoid predators, as terns do (Hatch,2002), or in response to annual snow and ice patterns. IfRoss’s gulls were breeding in Penny Strait in the years thatwe recorded none, they may have used low, wet, mainlandsites that we did not search (habitat more typical of theirSiberian breeding conditions; Densley, 1991), or theirnests could have failed before we arrived. It is also possi-ble that the gulls may not breed every year, perhapsinfluenced by food supplies, but at present we lack data toevaluate these various hypotheses.

Our observations of nest structure, eggs, and parentalbehaviour are markedly similar to those of Densley (1991),who examined nesting Ross’s gulls in Siberia. However,most of the nests we found had two eggs, whereas themodal clutch size at the Siberian colony was three eggs.Unfortunately, we could not return to the island to deter-mine nesting success.

Ross’s gulls nest in a range of habitat types, from inlandmarshy wetlands along coastal lowlands to gravel reefs(Blomqvist and Elander, 1981). The former habitat isabundant along the coast of Hudson Bay and in FoxeBasin, both areas where human contact is exceedingly low,but gulls have occasionally been observed during thebreeding season (Alvo et al., 1996; Béchet et al., 2000).Gravel reefs, such as those in Penny Strait, appear to bemore limited in the Canadian Arctic, and further surveysfor Ross’s gull colonies will likely be more successful iffocused on suitable coastal lowlands. In support of thishypothesis, we cite the fact that Ross’s gulls were knownto many Inuit who participated in traditional knowledgeinterviews in southern Baffin Island (Mallory et al., 2001),an area where gulls reared in Foxe Basin or migrating fromfarther north might be observed.

FIG. 1. Confirmed breeding locations of Ross’s gulls in North America andWest Greenland are shown as black dots. The star indicates the new colonylocation in Penny Strait.

ROSS’S GULLS IN PENNY STRAIT • 321

ACKNOWLEDGEMENTS

We thank Environment Canada (Canadian Wildlife Service),Natural Resources Canada (Polar Continental Shelf Project), andthe Nunavut Wildlife Management Board for financial and logisticsupport. Thanks also to C. Anderson, C. Lavalée, and M. Waylandfor field assistance; to J. Akearok for producing the map; and tothree referees for constructive comments on the manuscript.

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